Anti-caking composition for linear alkyl aryl sulfonate detergents



United States Patent 3,533,944 ANTI-CAKING COMPOSITION FOR LINEAR ALKYL ARYL SULFONATE DETERGENTS Shao-Yuen Yuan, San Rafael, Califi, assignor to Chevron Research Company, San Francisco, Calif., a corporation of Delaware No Drawing. Continuation of application Ser. No.

535,318, Mar. '18, 1966. This application Dec. 23,

1968, Ser. No. 786,860

Int. Cl. C09k 3/00 U.S. Cl. 252-383 2 Claims ABSTRACT OF THE DISCLOSURE A process for producing an alkali sulfosuccinate solution useful in providing anti-caking properties to detergents by reacting an approximately stoichiometric amount of sulfur dioxide with a concentrated solution of a disodium or dipotassium maleate while maintaining the pH of the solution within limits of 4 to 11 and heating the solution between 150 F. and 250 F. for a time sufficient to essentially complete the reaction.

This is a continuation of application Ser. No. 535,318 filed Mar. 18, 1966 and now abandoned.

This invention relates to an additive composition usefill in suppressing the tackiness or caking properties of straight-chain alkyl benzene sulfonate detergents and to a process for producing the additive composition.

Because of the biological hardness of branched-chain alkyl benzene sulfonate detergents, such as the polypropylene benzene sulfonates, the detergent industry has for the most part substituted straight-chain alkyl benzene sulfonates for po1ypropylene benzene sulfonates in the solid detergent formulations which are widely marketed at the present time.

It has been observed that the straight-chain or linear alkyl benzene sulfonates exhibit undesirable properties of tackiness or stickiness. During the manufacturing process the detergent tends to stick to process equipment, causing charring, and plugging of flow lines of the processing units and, after the detergent is packaged, it exhibits a strong tendency to cake during storage.

The use of sodium sulfosuccinate or potassium sulfosuccinate in straight-chain alkyl benzene sulfonates produces significant beneficial results. To illustrate, when drying the neutralized slurry of alkyl benzene sulfonic acids, the presence of the sulfosuccinate inhibits or prevents the formation of lumps and charring. These desirable effects are probably due to a more rapid rate of drying when the sulfosuccinate is present.

Further, the addition of a small amount of sulfosuccinate, preferably in the form of a slightly basic concentrated solution of sodium sulfosuccinate or potassium sulfosuccinate, improves built and unbuilt detergent composition. Incorporation of sulfosuccinate in a detergent formulation whrich typically may consist of 15 to 30 parts straight chain alkyl benzene sulfonate, 30 to 50 parts of sodium tripolyphosphate, 5 to parts of sodium silicate and to parts of sodium sulfate plus optional additives such as foam boosters, optical bleaches and perfumes, during the crutching step essentially eliminates the problems arising out of the tackiness property of the straight-chain alkyl benzene sulfonate during the manufacturing process and suppresses the tendency of the finished detergent to cake upon storage.

Patented Oct. 13, 1970 The quantity of slightly basic sulfosuccinate added is ordinarily in an amount sufficient to give the finished detergent a sulfosuccinate content in the range 2 to 25% by Weight based on the straight-chain alkyl benzene sulfonate content of the finished detergent.

The sulfosuccinate additive composition may be in the dry form or can be a concentrate in the form of an aqueous solution having a sulfosuccinate content" above about 30% by weight and containing a minor amount of dissolved basic reacting material sufiicient to give the solution a pH of at least about 8.5. The upper pH limit is not critical and can be 13 and higher; usually the pH ranges from about 8.5 to 10.

The basic reacting material is preferably a material selected from the group consisting of sodium hydroxide and potassium hydroxide. However, any basic reacting material, for example, a basic salt, such as sodium maleate, which, when added in small amounts will give the desired pH to the concentrate and which is chemically unreactive with the several components of the finished detergent may be used.

Broadly, in one embodiment of the invention, there is produced a concentrated aqueous solution of disodium maleate. To this solution there is added approximately a stoichiometrically equivalent quantity of sulfur dioxide while maintaining the pH in about the range 4 to 11. Upon addition of the sulfur dioxide, the reaction mixture is heated to ensure completion of the reaction between the maleate and the sulfur dioxide. The concentration of the final solution is adjusted to a sulfosuccinate content above about 30% by weight.

More specifically the compositions of the present invention are prepared by contacting a suitable base, hereinafter typified by sodium hydroxide, and maleic acid, under conditions to neutralize completely the carboxyl groups of the maleic acid. In carrying out this step a 50% by weight solution of sodium hydroxide is satisfactory. Enough sodium hydroxide is added to achieve a pH above 7, but usually a pH not exceeding about pH 10. Since the reaction is exothermic, care is taken that the temperature does not rise unduly, i.e., to a point where undesirable color bodies are formed. In general, a temperature within the range of about l30150 F. is maintained during this step.

There is then added liquid sulfur dioxide in proportions sufficient to neutralize excess sodium hydroxide and to provide an equimolecular proportion with respect to the maleic acid. Here, also the pH is maintained above 4 and generally between 4 and 11, and preferably about 6. To control the pH, additional sodium hydroxide may be introduced into the reaction zone simultaneously with the S0 Reaction temperatures are such as to effect sulfonation of the maleic acid, a reaction temperature in about the range -145 F. being satisfactory.

Following the introduction of the S0 the temperature is increased to ensure completion of the reaction, a temperature in the range l50250 F., preferably -180" F., for a period of one-half to two hours, is satisfactory.

The reaction mixture is then cooled, and if desired additional maleic anhydride may be added to react with any free sulfur dioxide.

When proceeding as above described solutions or concentrates can be prepared, which solutions consist essentially of water, at least 30% by weight of sodium sulfosuccinate and a minor amount of compatible basic reacting compound to give the solutions a pH of at least about 8.5. The proportion of sulfosuccinate will of course vary with the amount of water introduced with the basic solution, and to obtain concentrates of solutions of about at least 30 to 45% sulfosuccinate. Above about 45%, slurries of sodium sulfosuccinate in water are obtained. The proportion of water present during reaction will range from about one to three times the weight of maleic anhydride. As is known in the art, the desired proportion of water can be effected by varying the concentration of sodium hydroxide solution used in the reaction.

Solutions prepared in a manner described above can be dried, as in a rotary drum drier or spray drier, to facilitate shipping, the dried compositions being then reconstituted if desired.

A satisfactory composition may be prepared as follows:

EXAMPLE 1 A kettle fitted with a stirring means and a temperature measuring device and with appropriate inlet and outlet connections was charged with 4850 pounds (60.7 mols) of 50% sodium hydroxide and 8085 pounds of water. To this caustic solution there was added 2970 pounds (30.3 mols) of maleic anhydride. The anhydride was added at such a rate as to maintain the temperature between 130 F. and 150 F. Liquid sulfur dioxide was added to the resulting solution at the rate of 1500 pounds per hour. This addition was continued until a total of 2033 pounds (31.8 mols) had been charged. Simultaneously, 50% sodium hydroxide solution was added at such a rate as to maintain the pH between 7 and 8. In this manner, 2510 pounds (31.3 mols) of additional sodium hydroxide was added. The temperature of the reaction was held in the range of 135145 F.

When all of the above materials were charged, the reactor was heated to 175180 F. for an additional hour. It was then cooled to 130 F., and 60 pounds (0.6 mol) of maleic anhydride was added. The reactor contents were once again heated at 175180 F. for one hour. After cooling to room temperature, there was obtained 20,400 pounds of solution which analyzed as follows:

Specific gravity at 77 F. 1.345 Sodium sulfosuccinate, percent by weight (7950 pounds) 39 Sodium maleate, percent by weight (122 pounds) 0.6 pH 8.6

The reaction involved in the above procedure is as follows:

Sodium Sulfosuccinate (Trisoclium salt of ethane-1. Z-dicar boxylic l-sulfonic acid) EXAMPLE 2 In a 2-liter flask equipped with stirrer, thermometer and reflux condenser there was charged 516 g. of Water and 320 g. (4.0 mols NaOH) of 50% caustic. Molten maleic anhydride, 196 g. (2.0 mols) was then charged to the rapidly stirred caustic solution. The temperature rose to 150 F. during this addition. After the addition of all of the anhydride, the pH was 11.5.

S0 128 g. (2.0 mols) was charged to the above solution over a period of 45 minutes. Simultaneously, 50% caustic was added at such a rate as to maintain the pH at 6.2-6.3. A total of 160 g. (2.0 mols NaOH) was added with the S0 During this reaction the temperature was held at 202-214 F. After cooling to room temperature, the pH was adjusted to 9.1 by the addition of a few drops of 50% caustic.

Final concentration was 38% sodium sulfosuccinate by nuclear magnetic resonance analysis. No sodium maleate was found by this analysis.

The aqueous solution was divided into two equal parts, Parts (a) and (12). Part (a) was vacuum stripped to give a slurry containing solids. This slurry was filtered, and the solid precipitate was dried in a vacuum oven. Part (b) was placed directly in the facuum oven and dried. The solids from part (a) were used to prepare a 34% solution of sodium sulfosuccinate by dissolving 34 parts in 66 parts of tap water. This solution had a pH of 9. The solids of part (b) were used to prepare a 32% solution which also had a pH of 9.

Equally effective additive concentrates can be prepared substituting potassium hydroxide for sodium hydroxide in the preparation described above.

As an example of the preparation of potassium sulfosuccinate, 9.8 parts of maleic anhydride was placed in a beaker with 25 parts of distilled water. The resulting solution was made basic with 11.2 parts of potassium hydroxide dissolved in 22.5 parts water while maintaining efiicient stirring and cooling. To this solution there was added 6.4 parts of S0 and the pH was maintained between 7 and 8 by addition of potassium hydroxide in portions. The resulting solution was heated at 248 F. for one hour. The pH was adjusted to 9 by addition of 10% potassium hydroxide, after which the solution was drum dried to give tripotassium sulfosuccinate admixed with a small amount of potassium hydroxide.

Tabulated below are given a number of dried compositions which when reconstituted in water give solutions having the indicated pH.

TABLE I.TYPICAL SULFOSUCGINATE COMPOSITIONS AND pH OF THEIR SOLUTIONS The basic sulfosuccinate concentrate described in Example 1 above was employed in a commercial run in which a C C straight-chain alkyl benzene was sulfonated, neutralized with caustic, mixed with sodium tripolyphosphate and sodium silicate, crutched and spray dried. The additive concentrate was introduced during the crutching step an was introduced in an amount sufiicient to give the finished detergent a sulfosuccinate content of 2.5% by weight (10% by weight based on the sodium alkyl benzene sulfonate contained in the detergent). The plant had been experiencing line plugging due to tackiness before introduction of the basic sulfosuccinate additive was commenced. Promptly following introduction of the basic sulfosuccinate additive, tackiness disappeared and the process equipment and packaging lines ran smoothly.

I claim:

1. A process for producing a concentrated solution of alkali sulfosuccinates comprising:

(A) reacting an approximately stoichiometric amount of sulfur dioxide with a concentrated aqueous solution of a dialkali maleate selected from the group consisting of dipotassium and disodium maleate;

(B) maintaining the pH of said solution Within the 6 range of 4 to 11 by the addition of sodium or potas- OTHER REFERENCES sium hydroxide; and d h 1 R h M 1961 (C) heating said solution to a temperaturein the range ensed C emlca lcuonary em 0 p abut.150 R4500 a sufiiclent to cause Cotton and Wilkinson, Inorganic Chemistry, Advanced, essentlally complete reaction between the maleate Interscience chapterzl p. 546 1962. and sulfur dioxide. 5 2. A process as in claim 1, wherein said heating time LEON D. ROSDOL Primary Examiner f 1 2h ranges mm /2 to Ours I. GLUCK, Assistant Examiner References Cited .R. UNITED STATES PATENTS 10 252 138 61 3 4 2 6 0 1 X 3,328,314 6/1967 Marquis. 5 1 3 5l3 

